Time Domian Electron Paramagnetic Resonance Imaging

项目1：时域电子顺磁共振成像：仪器：可编程定时单元：EPR成像在任何给定频率下所需的射频脉冲的时间分辨率要求在纳秒范围内的时间分辨率，这与相同频率下的MRI实验不同。这是因为与核自旋动力学相比，顺磁自旋系统的自旋动力学更快。用于管理射频电路的定时单元在商业上是不可用的。我们设计，测试并集成了一种具有纳秒时间分辨率的新型可编程定时单元，该单元使用LabView技术的RF电子新方法控制光谱仪中的所有RF模块。集成该单元大大简化了光谱仪的操作，因此一般用户可以在没有射频工程专业知识的情况下使用扫描仪。此外，增加的光谱仪使该单元体积更小，并降低了为新购买的开放式磁体系统建造的第二台光谱仪的成本。开放式磁体系统：目前用于所有研究的磁体是在1994年购买的，并且提供了可靠的性能。然而，小孔的尺寸和设计使得体内实验在动物的饲养、麻醉、静脉输液管等方面存在困难，并且在孔内进行空气处理以保持核心体温在37℃。为了克服这些困难，我们采购并安装了一个开放的磁铁系统，可以在水平平面上（X和y方向）双向访问，以便体内实验可以轻松进行。用相应的放大器对磁体和梯度线圈进行了校准，并完成了控制软件的编写。射频链已集成，系统已准备好运行。用于EPR - mri联合成像的龙门架：由于基于EPR的pO2图像缺乏解剖信息，解释氧图通常是模棱两可的。为了克服这一限制，我们开发了将EPR图像与MRI的解剖图像共同配准的策略。300 MHz的EPRI工作频率与7 t的MRI扫描仪工作频率相似，因此设计、测试和优化了两种模式下的通用谐振器和龙门，并用于EPRI和RI在不移动物体的情况下对物体进行顺序成像。这使得利用解剖引导更可靠地解释氧图成为可能。体内EPRI和MRI联合成像：EPR成像虽然不能提供解剖信息，但可以可视化肿瘤内氧浓度的分布。EPRI/MRI联合系统可以准确了解肿瘤解剖中缺氧核心的位置，并通过MRI结合血容量、血流量、水扩散等氧状态和其他功能对肿瘤生理进行多功能分析。构建了300 MHz脉冲EPR/氧成像系统，其中设计了射频线圈和门架，也可用于MRI。待测小鼠在EPR和MRI磁体之间转移，无需将小鼠从线圈中取出，从而可以可靠而简单地通过EPRI和MRI进行氧图的共配准。利用该EPR/MRI共配准系统，研究了肿瘤氧状态、其他参数（包括血液灌注、与肿瘤细胞度呈负相关的水扩散）、MR光谱与放射治疗输出之间的关系。图像重建：目前使用的EPRI图像重建算法适用于奔腾PC。目前的情况是，数据集是计算所需的空间分辨率和生理分辨率的pO2图像。重新组织获取的数据需要2小时的计算时间，另外计算每个体素的pO2值需要30分钟。这给处理常规收集的活体实验图像数据带来了巨大的负担。为了减少图像重建时间，我们获得了一个基于linux的四双核集群CPU，内存为2tb。目前，每当完成幻影/动物体内血氧仪实验时，采集机采集的三维血氧仪数据集都会通过网络I/O传输到Parallel Server。在每次实验期间创建一个唯一的索引文件，并由服务器用于构造PBS（并行批处理服务器）作业。通过机器的四个双核处理器自动运行多线程C程序，可以减少fid。使用自定义并行Matlab开发的图形用户界面（GUI）使用简化的数据集来查看网格图，并根据用户提供的输入参数重建浓度图像和氧气图像。时间复杂度现在已经大大降低到几分钟的量级。Windows PC客户机通过Samba （Session Message Block）连接和SSH （Secure Shell）连接到Linux服务器，使任何授权用户都可以运行GUI

Project 1: Time Domian Electron Paramagnetic Resonance Imaging: Instrumentation: Programmable Timing Unit: The time resolution of the radiofrequency pulses needed in EPR Imaging at any given frequency requires time resolution in nanosecond range unlike MRI experiments at the same frequency. This is because of the faster spin dynamics of paramagnetic spin systems compared to nuclear spin dynamics. The timing unit to manage the RF circuitry is not available commercially. We have designed, tested, and integrated a novel programmable timing unit with nanosecond time resolution which controls all the RF modules in the spectrometer using a new approach in RF electronics utilizing LabView technology. Integrating this unit resulted in simplifying the spectrometer operation significantly so that general purpose users can use the scanner without RF engineering expertise. In addition, this addition to the spectrometer made the unit less bulky and decreased the cost of the second spectrometer being built for the newly purchased open magnet system. Open Magnet System: The currently used magnet for all the studies was purchased in 1994 and has provided reliable performance. However, the small bore size and design makes in vivo experiments difficult in terms of housing the animal and have the anesthesia, iv lines etc and the air handling in the bore to maintain the core body temperature at 37 C. To overcome these difficulties, we have procured and installed an open magnet system with access in both directions in the horizontal plane (X- and Y-directions) so that in vivo experiments can be performed with ease. The magnet and gradient coils have been calibrated with the corresponding amplifiers and the control software completed. The RF chain is integrated and the system is ready for operation. Gantry for EPRI-MRI combined imaging: Since EPR based pO2 images lack anatomic information, interpreting the oxygen maps is often equivocal. To overcome this limitation, we have developed strategies for co-registering the EPR Images with anatomic images from MRI. The frequency of operation in EPRI of 300 MHz is similar to that of an MRI scanner operating at 7 T. Therefore a common resonator and gantry were designed, tested, optimized for operation in both modalities and used for sequential imaging of the object with EPRI and RI without moving the object. This made it possible to interpret the oxygen maps more reliable utilizing the anatomic guidance. In Vivo EPRI and MRI Co-Imaging: EPR imaging can visualize the distribution of oxygen concentration in tumor, though it doesnt provide anatomical information. The combined system of EPRI/MRI makes it possible to know the exact location of hypoxic core in the tumor anatomy, and also multi-functional analysis of tumor physiology combining the oxygen status and other functions by MRI including blood volume, blood flow, water diffusion etc. 300 MHz pulsed EPR/oxygen imaging system was constructed in which the RF coil and gantry were designed to also be used for MRI. The mouse to be measured is transferred between EPR and MRI magnets without removing the mouse from the coil, making reliable and simple co-registration of oxygen map by EPRI and anatomy by MRI possible. Using this EPR/MRI co-registration system, the relationship among tumor oxygen status, other parameters including blood perfusion, water diffusion which inversely related with tumor cellularity, MR spectroscopy, and resulting output of radiation therapy is underway. Image Reconstruction: The currently used EPRI image reconstruction algorithms are adapted on a Pentium PC. The current situation is that the data sets are to calculate the pO2 images with the required spatial and physiological resolutions. It takes 2 hours computational time to reorganize the acquired data and an additional 30 minutes to calculate the pO2 values in each voxel. This imposes enormous burden to process routinely collected image data from in vivo experiments. To reduce the image reconstruction time, we have acquired a Linux-based four dual-core cluster CPU with a 2 TB memory. Currently, whenever the phantom/animal in-vivo oximetry experiment is completed, the 3-D oximetry data sets that are collected in the collection machine are transferred to the Parallel Server via network I/O. A unique index file is created during every experiment and used by the server to construct PBS (Parallel Batch Server) job. The FIDs are reduced by automatically running a multi-threaded C program by the four dual-core processors of the machine. A graphical user interface (GUI) developed using custom parallel Matlab, uses the reduced data sets to view the mesh plots and to reconstruct the concentration images and oxygen images depending upon the input parameters provided by the user. The time complexity has now drastically reduced in the order of few minutes. A Windows PC client to Linux server connection via Samba (Session Message Block) connectivity and SSH (Secure Shell) enables any authorized users to run the GUI